The action spectrum is the spectrum of light which correlates to biological activity. For example, in 1881, Thomas W.. Engelmann learned that the green algae spirogyra undergoes photosynthesis most effectively when exposed to red and blue light. Melatonin suppression, a physiological activity involved in the regulation of the pineal gland, is another example of an action spectrum. Light suppression of melatonin secretion takes place at specific wavelengths.
- Action and Absorption Spectra J. Kimball, (2001) Biology Pages
- Brainerd GC, Hanifin JP, Greeson, JM, Byrne B, Glickman G, Gerner E, Rollaq MD (2001) Action spectrum for melatonin regulation in humans: Evidence for a novel circadian photoreceptor. Journal of Neuroscience, August 15; 21(16):6405-6412.; An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans Thapan K, Arendt J, Skene DJ (2001) Journal of Physiology, August 15 Volume 535, Number 1, 261-267.